This application is filed under 35 U.S.C. xc2xa7371 from International Application PCT/JP00/01544, with an international filing date of Mar. 14, 2000, which claims the benefit of priority to Japanese Application Nos.: 11-88157, filed Mar. 30, 1999; 11-98179, filed Apr. 5, 1999; 11-254941, filed Sep. 8, 1999; 2000-25373, filed Feb. 2, 2000; and, 2000-25386, filed Feb. 2, 2000, which are incorporated by reference in their entirety.
1. Field of the Invention
The present invention relates to a polishing body used in a polishing apparatus which is suitable for use in planarization polishing, etc., of semiconductor devices such as ULSI devices, etc., performed in processes in which such semiconductor devices are manufactured, a polishing apparatus and a polishing method, and further relates to a semiconductor device manufacturing method using the above-mentioned polishing apparatus and polishing method.
2. Discussion of the Related Art
As semiconductor integrated circuits have become finer and more highly integrated, the individual processes involved in semiconductor manufacturing processes have become more numerous and complicated. As a result, the surfaces of semiconductor devices are not always flat. The presence of step differences on the surfaces of semiconductor devices leads to step breakage of wiring and local increases in resistance, etc., and thus causes wiring interruptions and drops in electrical capacitance. In insulating films, furthermore, such step differences also lead to a deterioration in the withstand voltage and the occurrence of leaks.
Meanwhile, as semiconductor integrated circuits have become finer and more highly integrated, the wavelengths of light sources in semiconductor exposure apparatuses used in photolithography have become shorter, and the numerical aperture or so-called NA of the projection lenses used in such semiconductor exposure apparatuses has become larger. As a result, the focal depth of the projection lenses used in such semiconductor exposure apparatuses has become substantially shallower. In order to deal with such increasing shallowness of the focal depth, there is a demand for even greater planarization of the surfaces of semiconductor devices than that achieved so far.
To describe this in concrete terms, planarization techniques such as that shown in FIG. 1 have become essential in semiconductor manufacturing processes. FIG. 1 is a schematic diagram illustrating planarization techniques used in a semiconductor manufacturing process, and shows sectional views of a semiconductor device. In FIG. 1, 11 indicates a silicon wafer, 12 indicates an inter-layer insulating film comprising SiO2, 13 indicates a metal film comprising Al, and 14 indicates the semiconductor device.
FIG. 1A shows an example of the planarization of an inter-layer insulating film 12 on the surface of the semiconductor device. FIG. 1B shows an example in which a so-called damascene is formed by polishing a metal film 13 on the surface of the semiconductor device. A chemical mechanical polishing or chemical mechanical planarization (hereafter referred to as xe2x80x9cCMPxe2x80x9d) technique is widely used as a method for planarizing the surfaces of such semiconductor devices. Currently, the CMP technique is the sole method that can be used to planarize the entire surface of a silicon wafer.
CMP was developed on the basis of silicon wafer mirror surface polishing methods, and is performed using a CMP apparatus of the type shown in FIG. 2. In FIG. 2, 15 indicates a polishing member, 16 indicates a member that holds the object of polishing (hereafter referred to as a xe2x80x9cpolishing headxe2x80x9d in some instances), 17 indicates a silicon wafer which is the object of polishing, 18 indicates a polishing agent supply part, and 19 indicates a polishing agent. The polishing member 15 has a polishing body 21 (hereafter referred to as a xe2x80x9cpolishing padxe2x80x9d in some instances) which is attached to the surface of a polishing platen 20. A sheet-form foam polyurethane is widely used as such a polishing body 21.
The object of polishing 17 is held by the polishing head 16, so that it is caused to oscillate while being rotated, and is pressed against the polishing body 21 of the polishing member 15 with a specified pressure. The polishing member 15 is also rotated, so that a relative motion is performed between the polishing member 15 and the object of polishing 17. In this state, the polishing agent 19 is supplied to the surface of the polishing body 21 from the polishing agent supply part 18. The polishing agent 19 diffuses over the surface of the polishing body 21, and enters the space between the polishing body 21 and the object of polishing 17 as the polishing member 15 and object of polishing 17 move relative to each other, so that the surface of the object of polishing 17 that is to be polished is polished. Specifically, good polishing is accomplished by a synergistic effect of the mechanical polishing caused by the relative motion of the polishing member 15 and object of polishing 17 and the chemical action of the polishing agent 19.
In cases where a sheet-form polishing pad comprising a conventional foam resin (hereafter referred to as a xe2x80x9cfoam polishing padxe2x80x9d) is used, the uniformity of the polishing over the entire surface of the wafer is good. However, foam polishing pads generally suffer from the following problems:
(1) The edge sloping that occurs in polishing is great.
(2) When a load is applied, the pads undergo compressive deformation.
As a result of these problems, foam polishing pads have not shown good step difference elimination characteristics, i.e., good polishing smoothness, in the case of patterned wafers. Recently, therefore, polishing pads comprising harder non-foam resins (hereafter referred to as xe2x80x9cnon-foam polishing padsxe2x80x9d in some instances) have been investigated.
In non-foam polishing pads, indentations and projections comprising a groove structure are formed in the surface of a hard macromolecular polymer, and these indentations and projections polish the surface of the object of polishing (in this case, a wafer). The use of a non-foam polishing pad solves the problem of poor step difference elimination characteristics encountered in cases where foam polishing pads are used.
In regard to the process stability of a CMP apparatus, an absence of scratches is required from the standpoint of avoiding wiring interruption and insulation breakdown of the device, in addition to the requirement for stable uniformity and smoothness even when the number of wafers treated by the polishing pad is increased.
However, although hard polishing pads comprising non-foam resins show good pattern step difference elimination, such pads tend to cause scratching of the wafer; furthermore, the polishing rate tends to be lower than that of polishing pads comprising a foam polyurethane.
Furthermore, other important factors that generally determine the polishing rate of a polishing pad include the retention and fluidity of the polishing agent on the surface of the polishing pad. In terms of retention of the polishing agent, hard non-foam polishing pads cannot match foam polishing pads. Furthermore, in cases where conventional non-foam polishing pads are fastened to the surface of a platen, and this platen is rotated at a high speed while the polishing agent is supplied, the polishing agent is caused to fly off the polishing pad by centrifugal force, so that the polishing agent retention is low. Accordingly, there is a problem in that the polishing agent that is supplied does not effectively contribute to an increase in the polishing rate.
Meanwhile, the most commonly used polishing body in conventional processes is a polishing body (polishing pad) which chiefly comprises a foam polyurethane. Such a polishing body has a superior capacity for retaining the polishing agent on the surface of the polishing body. However, when such a polishing body is continuously used, the abrasive particles of the polishing agent clog the holes in the foam portion of the surface of the polishing body, so that there are large fluctuations in the polishing rate. Accordingly, an operation known as xe2x80x9cdressingxe2x80x9d, in which the surface of the polishing body is ground away by means of a grinding wheel on which diamonds have been electrodeposited must be performed before polishing and during polishing, so that the surface conditions of the polishing body always remain the same.
Furthermore, like the above-mentioned foam polishing bodies, fixed abrasive particle type polishing bodies in which polishing abrasive particles are contained in a resin also require dressing in order to handle clogging of the holes in the foam portion by abrasive particles and in order to keep the state of the polishing abrasive particles uniform.
In regard to the polished silicon wafer (object of polishing), the polishing characteristics of uniformity and smoothness are extremely important.
xe2x80x9cUniformityxe2x80x9d is used to evaluate how uniformly polishing is performed over the entire area of the silicon wafer. The following formula is generally used for this evaluation:
Uniformity (%)=(RAxe2x88x92RI)/(RA+RI)xc3x97100
Here, RA is the maximum amount of polishing in the measured polishing amount profile, and RI is the minimum amount of polishing in the measured polishing amount profile. In the case of the uniformity value obtained from the above formula, a smaller value indicates better characteristics. Specifically, the uniformity of polishing over the entire surface of the silicon wafer increases with a decrease in the difference between the maximum amount of polishing and the minimum amount of polishing.
Furthermore, xe2x80x9csmoothnessxe2x80x9d is used to evaluate the magnitude of the residual step difference when a pattern with indentations and projections is polished. In other words, in a patterned silicon wafer with step differences, this value indicates the extent to which projecting parts of the patterned silicon wafer are selectively polished away by polishing, so that the residual step differences following polishing are reduced.
Both of these polishing characteristics of uniformity and smoothness are very greatly influenced by the elastic modulus of the polishing body. Polishing bodies are classified according to the size of their elastic modulus into soft polishing bodies which have a small elastic modulus and hard polishing bodies which have a large elastic modulus.
In the case of soft polishing bodies, the adhesion of the surface of the polishing body to warping of the silicon wafer is extremely high when pressure is applied to the silicon wafer, so that the uniformity is extremely good over the entire surface of the silicon wafer. However, in the case of silicon wafers with recessed and projecting patterns, the polishing body conforms to the indentations and projections in the surface of the silicon wafer as a result of the deformation of the polishing body, so that polishing proceeds with the step differences remaining unchanged. As a result, the smoothness is poor.
On the other hand, in the case of hard polishing bodies with a large elastic modulus, the deformation of the polishing body with respect to silicon wafers that have an recessed and projecting pattern is small, so that polishing proceeds in order from the projecting portions of the recessed and projecting pattern; as a result, the smoothness is good. However, since the warping of the silicon wafer and the pressure distribution during pressure application have a direct effect on the polishing, the uniformity is poor.
However, even in cases where the same material is used for the polishing body, the thickness of the polishing body and structural factors of the polishing body such as the width and depth of the grooves in the surface of the polishing body have a great effect as variations in the apparent elasticity. Specifically, as the thickness of the polishing body increases, the amount of elastic deformation of the polishing body increases, so that the polishing body becomes softer in apparent terms. On the other hand, in the case of a thin polishing body, the amount of deformation is small, so that the polishing body is hard in apparent terms. Furthermore, in terms of the groove structure as well, a polishing body in which the depth of the grooves is deep and the width of the projection portions between the grooves is narrow shows a large deformation of the surface when the load is applied, so that such a polishing body is soft in apparent terms. On the other hand, a polishing body in which the depth of the grooves is shallow and the width of the projecting portions between the grooves is wide shows little deformation when the load is applied, so that such a polishing body is hard in apparent terms.
In the above description, the thickness and groove structure of the polishing body were described from the standpoint of elasticity. Besides this, another important role played by the grooves is the stable supply of the polishing agent. In regard to groove structures for achieving such a stable supply of the polishing agent, groove patterns of various shapes have been disclosed in the past. If the supply of the polishing agent that is accomplished by means of these grooves is insufficient, the polishing agent that is supplied to the surface of the object of polishing that is being polished will be insufficient, so that the mechanical polishing and the chemical reaction that occurs during polishing are insufficient. As a result, the polishing rate drops. Furthermore, the temperature conditions resulting from the friction between the polishing body and the surface of the object of polishing that is being polished are also non-uniform, so that there is a conspicuous drop in the uniformity of the polishing; moreover, such a problem also leads to scratching of the surface of the object of polishing and vibration of the polishing head and polishing platen during polishing, etc.
Polishing apparatuses used to perform CMP include various types of apparatuses based on different concepts and with different special features. For example, such apparatuses include apparatuses in which a plurality of silicon wafers are simultaneously polished by means of a single polishing body in order to increase the throughput, apparatuses in which polishing is performed by high-speed rotation using a polishing body that is smaller than the silicon wafer in order to reduce the size of the apparatus, and apparatuses in which the polishing head part is specially modified in order to improve the uniformity, etc. Such diversity of polishing apparatuses has an inseparable relationship with the optimal groove structure for a stable supply of the polishing agent, and such a stable supply of the polishing agent to the polishing surface depends largely on the apparatus that is used.
In CMP, the polishing working time is extremely short compared to that of other types of polishing such as optical polishing or metal lapping, etc. Specifically, polishing is performed under conditions in which the rotation and application of pressure, etc., during polishing are extremely great. Accordingly, polishing is performed under conditions in which retention of the polishing agent on the surface of the polishing body is difficult.
In regard to the groove structure that is considered optimal, the above-mentioned dependence on the apparatus may be cited; basically, however, what is important is how the polishing agent should be retained on the surface of the polishing body during polishing.
However, in the case of conventional polishing bodies that chiefly comprises a foam polyurethane, and fixed abrasive particle type polishing bodies in which the polishing abrasive particles are contained in a resin, the surface of the polishing body is shaved away by dressing, so that the thickness of the polishing body gradually decreases. Accordingly, in a case where the polishing body is viewed as a single elastic body, since the thickness changes, the polishing body shows a continuous variation in the amount of elastic deformation accompanying this change in thickness, thus resulting in the problem of a large fluctuation in the uniformity and smoothness as the polishing body is used. Furthermore, not only does the thickness of the above-mentioned polishing body vary as a result of dressing, but there is also a change in the groove structure (depth of the grooves, etc.) in the surface of the polishing body. As a result, another problem arises: namely, the polishing characteristics cannot be controlled by means of the thickness and groove structure of the polishing body.
As was described above, an improvement in uniformity and an improvement in smoothness cannot both be achieved at the same time in either soft polishing bodies or hard polishing bodies; there is a tradeoff relationship between uniformity and smoothness.
Recently, polishing bodies which have a laminated structure in which two layers, i.e., a lower layer with a large elastic modulus and an upper layer with a small elastic modulus, are laminated have been used in order to satisfy both of the above-mentioned polishing requirements; furthermore, polishing heads with a fluid pressurization system, etc., in which the pressure application system of the polishing head is modified have been used with the aim of achieving both an improvement in uniformity and an improvement in smoothness.
However, in the case of polishing bodies with a laminated structure, there are great differences in the polishing characteristics due to variation in the polishing bodies themselves, so that the problem of an increase in unstable elements is encountered from the standpoint of semiconductor manufacturing processes. Furthermore, in cases where the polishing head is modified, the problem is that the structure of the polishing head becomes extremely complicated.
A first aspect of the present invention is to solve the above-mentioned problems, and more concretely, to provide a polishing body (polishing pad), polishing apparatus and polishing method in which scratching tends not to occur, and in which the polishing rate is high, and a semiconductor device manufacturing method using the above-mentioned polishing apparatus and polishing method.
A second aspect of the present invention is to solve the above-mentioned problems, and more concretely, to provide a non-foam polishing body (polishing pad) in which the supplied polishing agent contributes effectively to polishing, so that efficient polishing is possible with respect to the polishing agent supply, in which the retention and fluidity of the polishing agent are high, so that the polishing rate is high, in which there is little scratching, and which is superior in terms of step difference elimination, as well as a polishing apparatus and polishing method using the above-mentioned polishing body, and a semiconductor device manufacturing method in which the cost of the polishing process is reduced and a more efficient process is achieved as a result of the use of the above-mentioned polishing apparatus and polishing method, and in which semiconductor devices can therefore be manufactured at a lower cost than in conventional semiconductor device manufacturing methods.
A third aspect of the present invention is to solve the above-mentioned problems, and more concretely, to provide a polishing body in which the wear caused by use of the polishing body is extremely small, and there is little variation in the surface shape, so that the polishing body always has stable polishing characteristics, a polishing apparatus and polishing method using this polishing body, and a semiconductor device manufacturing method using this polishing apparatus and polishing method.
Furthermore, another aspect is to provide a polishing body in which the polishing characteristics of uniformity, smoothness and polishing rate of the object of polishing can be controlled, and a polishing apparatus using this polishing body.
A fourth aspect of the present invention is to solve the above-mentioned problems, and more concretely, to provide a polishing body (polishing pad) which shows superior characteristics in terms of both uniformity and smoothness even in a conventional polishing apparatus, a polishing apparatus and polishing method using this polishing body, and a semiconductor device manufacturing method using this polishing apparatus and polishing method.
A first embodiment of the present invention which is used in order to achieve the above-mentioned first aspect is a polishing body used in a polishing apparatus which is equipped with a polishing head that holds the object of polishing and a polishing body, and which polishes the object of polishing by causing relative motion between the polishing body and the object of polishing in a state in which a polishing agent is interposed between the polishing body and the object of polishing; the polishing body being characterized by the fact that at least the surface of the polishing body comprises a non-foam macromolecular polymer, a groove structure is formed in the surface, and the surface has no sharp edge parts.
First, as a result of investigating polishing pads themselves, it has been discovered that there are problems in the groove structure formed in the surfaces of hard polishing pads comprising non-foam resins. When this groove structure is formed, flash may be formed on the surface of the polishing pad. Such flash may also be stripped away during polishing. This flash causes scratching of the surface of the object of polishing, i.e., the wafer. Furthermore, it was also discovered that the slurry may aggregate with such flash acting as nuclei, and that the aggregated slurry may cause scratching of the wafer surface.
The present invention was devised on the basis of such findings. Specifically, since the polishing body of the present invention comprises a non-foam macromolecular polymer, this polishing body retains the advantages of polishing bodies that comprise the non-foam agents; in addition, however, since this polishing body has no sharp edge parts on its surface, no flash is generated when these edge parts are formed. Accordingly, there is no scratching of the surface of the wafer caused by flashes or aggregation of the slurry. Furthermore, the term xe2x80x9cedge partxe2x80x9d refers to the boundaries between indentations and projections formed on the surface, and the apices of projecting parts. Furthermore, as is clear from the above description, the term xe2x80x9csharp edge partsxe2x80x9d refers to edge parts on which flash is generated during working, and which are sharp enough so that this flash is stripped away during polishing.
A second embodiment of the present invention which is used in order to achieve the first aspect is the first embodiment wherein the groove structure comprises a plurality of grooves which have a plurality of intersection points, and the angles at which the grooves cross at the intersection points do not include any sharp angles that are less than 2 degrees.
Grooves are ordinarily formed in the surface of a polishing body for the purpose of supplying the polishing agent to the space between the polishing body and the object of polishing, etc. As a result of further experiments, it has been discovered in the case of a polishing body using an ordinary non-foam macromolecular polymer, flash tends not to be generated during working if the angles of intersection of the groove are less than 2 degrees, and that even if flash is generated, there is little stripping of this flash during polishing, so that scratching of the object of polishing is greatly reduced, thus making such angles desirable. Accordingly, in the present invention, the angles of intersection at the intersection points of the grooves are limited to angles that are less than 2 degrees.
A third embodiment of the present invention which is used in order to achieve the first aspect is the first embodiment wherein the groove structure comprises a plurality of grooves that have a plurality of intersection points, and the groove portions do not have any edge parts with a curvature radius of less than 50 xcexcm.
As a result of additional experiments, it has been discovered that if sharp portions with a curvature radius of less than 50 xcexcm are present in the curved parts, intersection parts or corner parts of the grooves formed in the surface of the polishing body, flash is frequently generated in these portions during working, and this flash falls off during polishing. The present invention is based on this finding, and is characterized by the fact that there are no edge parts with a curvature radius of less than 50 xcexcm in the groove areas.
A fourth embodiment of the present invention which is used in order to achieve the first aspect is any of the first through third embodiments wherein the groove structure comprises one of a combination of a spiral groove and radial grooves, a combination of concentric circular grooves and radial grooves, and lattice-form grooves.
In the case of such groove structures, the angle of intersection of the spiral groove and radial grooves, concentric circular grooves and radial grooves or lattice-form grooves with each other can be set at close to 90 degrees. Accordingly, the generation of flash in the areas of intersection of the grooves during working can be inhibited, and such flash can be prevented from falling off during polishing.
A fifth embodiment of the present invention which is used in order to achieve the first aspect is any of the first through fourth embodiments wherein the macromolecular polymer comprises at least one resin selected from a set comprising epoxy resins, acrylic resins, polyester resins, vinyl chloride resins, polycarbonate resins and non-foam urethane resins.
Such materials show little wear during polishing. Accordingly, in cases where such materials are used for the polishing body, the useful life of the polishing body is extended. Consequently, the frequency with which the polishing body is replaced can be lowered, so that polishing costs can be reduced.
A sixth embodiment of the present invention which is used in order to achieve the first aspect is a polishing method in which a polishing head which holds the object of polishing, and a polishing body in which at least the surface of the polishing body comprises a non-foam macromolecular polymer, are used, and the object of polishing is polished by causing relative motion between the polishing body and the object of polishing in a state in which a polishing agent is interposed between the polishing body and the object of polishing, wherein the polishing agent contains cerium oxide particles.
Generally, slurries containing silicon dioxide (SiO2) are widely used as polishing agents in the CMP polishing of dielectric materials. Such slurries are superior in terms of stability, but tend to aggregate and form a glass. This aggregate forms on the surface of the polishing pad. In cases where the point at which the aggregate forms is located inside a groove, the aggregate does not cause scratching; however, in cases where the aggregate forms outside a groove, i.e., on a projecting part, this aggregate tends to cause scratching.
In contrast, a slurry containing cerium oxide readily disperses in water; furthermore, such a slurry can be washed away easily by means of water, and tends not to aggregate; accordingly, a slurry of this type is suitable for use on a hard polishing pad comprising a non-foam resin (hereafter referred to as a xe2x80x9cnon-foam polishing padxe2x80x9d). Accordingly, in the present invention, a polishing pad in which at least the surface of the pad comprises a non-foam macromolecular polymer is used as the polishing body, and a slurry containing cerium oxide particles is used as the polishing agent; as a result, the occurrence of cracking caused by the polishing agent can be prevented to a greater extent than in possible in polishing agents containing silicon dioxide.
In cases where a slurry of cerium oxide is used with a foam polishing pad, the force retaining the slurry in the foam of the working surface of the polishing pad is high, so that an excessive quantity of cerium abrasive particles remains, thus affecting the stability of the polishing. Specifically, in such cases, the problem of a variation in the polishing rate over time and the problem of a slow response with respect to the control of the slurry supply have been encountered. In contrast, the non-foam polishing pad used in the present invention has a low retention force, and does not drag out the effects of previous states; accordingly, the control of the slurry concentration is immediately reflected in the polishing characteristics, especially the polishing rate, so that stable polishing characteristics can be maintained.
Furthermore, in cases where a non-foam polishing pad and a silicon oxide slurry are combined, it is difficult to increase the polishing rate; however, a high polishing rate can be obtained by combining such a polishing pad with a cerium oxide slurry. Furthermore, in regard to the size of the cerium oxide particles, particles that are easily obtainable may ordinarily be used; generally, the particle size is 200 nm or smaller.
A seventh embodiment of the present invention which is used in order to achieve the first aspect is a polishing method in which a polishing head which holds the object of polishing, and a polishing body in which at least the surface of the polishing body comprises a non-foam macromolecular polymer, are used, and the object of polishing is polished by causing relative motion between the polishing body and the object of polishing in a state in which a polishing agent is interposed between the polishing body and the object of polishing, wherein the polishing agent contains cerium oxide particles, and the polishing body is the polishing body of any of the first through fifth embodiments.
In this invention, the effect whereby the polishing pad itself tends not to form flash, and the effect whereby the polishing agent does not cause scratching act in a synergistic manner, so that the effect that prevents scratching of the object of polishing during polishing is heightened.
An eighth embodiment of the present invention which is used in order to achieve the first aspect of the first embodiment is a polishing method in which a polishing head which holds the object of polishing, and a polishing body, are used, and the object of polishing is polished by causing relative motion between the polishing body and the object of polishing in a state in which a polishing agent is interposed between the polishing body and the object of polishing, wherein the method has a stage in which a load is gradually applied between the object of polishing and the polishing body.
Accordingly, in cases where a fixed load is applied between the object of polishing and the polishing body, the polishing torque during polishing rises abruptly immediately after the initiation of polishing, then drops abruptly after a few seconds and reaches a more or less constant value after approximately 10 seconds. Accordingly, if a polishing method has a stage in which a load is gradually applied between the object of polishing and the polishing body, the torque can be prevented from increasing abruptly immediately after the initiation of polishing. As a result, scratching of the object of polishing caused by such an abrupt increase in torque can be prevented. Furthermore, the load on the polishing apparatus is reduced; consequently, not only are the effects of vibration and heat reduced, but a superior effect is obtained which makes it possible to alleviate scratching that tends to occur in cases where a hard polishing pad is used.
A ninth embodiment of the present invention which is used in order to achieve the first aspect is a polishing method in which a polishing head which holds the object of polishing, and a polishing body, are used, and the object of polishing is polished by causing relative motion between the polishing body and the object of polishing in a state in which a polishing agent is interposed between the polishing body and the object of polishing, wherein the method has a stage in which the load between the object of polishing and the polishing body is adjusted so that one of the moving load of the object of polishing and the polishing body is constant.
In this invention as well, an abrupt increase in the torque immediately following the initiation of polishing can be prevented; as a result, scratching of the object of polishing caused by such an abrupt increase in the torque can be prevented. The load on the polishing apparatus is reduced even further; accordingly, not only are the effects of vibration and heat reduced even further, but a superior effect is obtained which makes it possible to achieve a further alleviation of scratching in cases where a hard polishing pad is used.
A tenth embodiment of the present invention which is used in order to achieve the first aspect is a polishing apparatus which is equipped with a polishing head which holds the object of polishing, and a polishing body, and in which the object of polishing is polished by causing relative motion between the polishing body and the object of polishing in a state in which a polishing agent is interposed between the polishing body and the object of polishing; this polishing apparatus being characterized by the fact that one of the polishing bodies of the first embodiment through fifth embodiment is used as the above-mentioned polishing body.
In this invention, one of the polishing bodies of the above-mentioned first embodiment through fifth embodiment is used as the polishing body; accordingly, the effects described for the respective inventions can be exhibited, so that the above-mentioned first aspect can be achieved.
An eleventh embodiment of the present invention which is used in order to achieve the first aspect is a polishing apparatus which is equipped with a polishing head which holds the object of polishing, and a polishing body, and in which the object of polishing is polished by causing relative motion between the polishing body and the object of polishing in a state in which a polishing agent is interposed between the polishing body and the object of polishing; this polishing apparatus being characterized by the fact that the apparatus is equipped with a load-applying mechanism which applies a variable load between the object of polishing and the polishing body, a polishing body moving mechanism which moves the polishing body, an object of polishing moving mechanism which moves the object of polishing, respective load detection mechanisms which are used to detect the load of the movement of the polishing body moving mechanism or the object of polishing moving mechanism, or both, and a feedback mechanism which is used to control the load applied by the load-applying mechanism on the basis of the load value detected by one of the load detection mechanisms.
Accordingly, as was described above, in cases where a fixed load is applied between the object of polishing and the polishing body, the polishing torque during polishing rises abruptly immediately after the initiation of polishing, then drops abruptly after a few seconds and reaches a more or less constant value after approximately 10 seconds. Furthermore, such an abrupt increase in the torque immediately after the initiation of polishing causes scratching of the object of polishing. In this invention, the polishing apparatus is equipped with respective load detection mechanisms which are used to detect the load of the movement of the polishing body moving mechanism or object of polishing moving mechanism, or both, and a feedback mechanism which is used to control the load applied by the load-applying mechanism on the basis of the load values detected by one of the load detection mechanisms. Accordingly, the load (torque) can always be maintained at an appropriate value. Consequently, scratching of the object of polishing caused by the increase in torque can be prevented.
A first embodiment of the present invention which is used in order to achieve the second aspect is a polishing body used in a polishing apparatus in which an object of polishing is polished by causing relative motion between a polishing body and this object of polishing in a state in which a polishing agent is interposed between the polishing body and object of polishing; this polishing body being characterized by the fact that at least the working surface part of the polishing body comprises a non-foam resin, and has a plurality of recessed and projecting parts comprising a groove structure, and this groove structure comprises a combination of one or more types of grooves selected from a set comprising concentric circular, spiral, lattice-form, triangular lattice-form and radial grooves.
As long as at least the working surface part of the polishing body in this embodiment has a groove structure comprising a non-foam resin, this polishing body may be a sheet-form or plate-form polishing body, a polishing body with a multi-layer structure in which different types of materials are laminated, or a plate-form polishing body molded on a rigid flat plate.
Furthermore, the shape of the grooves is important for increasing the polishing rate and eliminating scratches; for this reason, a pattern is selected which is suitable for ensuring the fluidity and retention of the polishing agent, and for effectively discharging polishing debris and aggregated polishing particles. Accordingly, such a pattern is preferably a combination comprising one or more types of grooves selected from a set comprising concentric circular, spiral, lattice-form, triangular lattice-form and radial grooves.
The polishing body of this embodiment is capable of performing polishing with an efficiency comparable to that of conventional foam polishing pads for the amount of polishing agent that is supplied; furthermore, since this polishing body is a hard polishing pad, it is superior in terms of eliminating step differences in patterned wafers.
A second embodiment of the present application which is used in order to achieve the second aspect is the first embodiment, which is further characterized by the fact that the sections of the recessed parts (groove parts) and projecting parts respectively have one or more shapes selected from a set comprising rectangular, trapezoidal and triangular shapes.
In this embodiment, since the sections of the recessed parts (groove parts) and projecting parts respectively have one or more shapes selected from a set comprising rectangular, trapezoidal and triangular shapes, the advantage of easy workability of the grooves to an optimal pitch and width is obtained.
A third embodiment of the present invention which is used in order to achieve the second aspect is the second embodiment which is further characterized by the fact that the rectangular, trapezoidal or triangular shapes satisfy the following conditions:
axe2x89xa7b, bxe2x89xa70, cxe2x89xa70
wherein, a is the length of the bottom sides of the projecting parts, b is the length of the top sides of the projecting parts, and c is the length of the bottom sides of the recessed parts.
As a result of the use of such a construction, clogging of the grooves during the discharge of polishing debris or aggregated polishing particles is eliminated, so that the discharge of such polishing debris or aggregated polishing particles to the outside of the working surface of the polishing body is smoothly accomplished. Accordingly, the polishing rate can be increased, and scratching of the object of polishing by polishing debris or aggregated polishing particles can be prevented. Furthermore, as a result of the use of such a construction, the merit of simplified working of the grooves is also obtained.
In the polishing body of this embodiment, the fluidity of the polishing agent and the size of the contact area are optimized, so that the polishing rate is rapid; furthermore, since this polishing body is a hard pad, it is superior in terms of elimination of step differences in patterned wafers. Moreover, since the width of the grooves is optimized, the discharge of polishing debris and aggregates of the polishing agent can be smoothly accomplished, and there is no scratching.
A fourth embodiment of the present invention which is used in order to achieve the second aspect is the third embodiment which is further characterized by the fact that the rectangular, trapezoidal or triangular shapes satisfy the following conditions:
0.0 mmxe2x89xa6bxe2x89xa63.0 mm, 0.1 mmxe2x89xa6a+cxe2x89xa65.0 mm, dxe2x89xa70.1 mm
wherein, d is the depth of the recessed parts.
The relationship between the amount of polishing of a silicon wafer and the polishing conditions is given by an empirical formula known as the formula of Preston, which is indicated by Equation (1).
R=kxc3x97Pxc3x97Vxe2x80x83xe2x80x83(1)
Here, R is the amount of polishing of the silicon wafer, P is the pressure per unit area with which the silicon wafer is pressed against the polishing body, V is the relative linear velocity caused by the relative motion between the polishing member and the silicon wafer, and k is a proportionality constant.
According to the formula of Preston, the polishing rate is proportional not only to the relative velocity between the polishing body and the object of polishing, but also to the pressure at the contact face between the object of polishing and the polishing body. Since the polishing rate is also proportional to the effective contact area, the polishing rate increases with an increase in the contact area at the same relative velocity and load per unit area. Here, the term xe2x80x9ceffectivexe2x80x9d in xe2x80x9ceffective contact areaxe2x80x9d refers to the fact that the contact area during polishing adopts an effective value that differs from the value that is simply calculated from the figures, since the state of contact between the polishing body and the object of polishing differs when no pressure is applied and when pressure is applied during polishing, and since the contact between the polishing body and the object of polishing is not perfect in some instances. In the case of a non-foam polishing pad, the polishing rate cannot be increased by means of a simple increase in the contact area, since the polishing agent is not supplied to every part of the above-mentioned contact face, i.e., since the fluidity of the polishing agent is low. The supply of the polishing agent to every part of the above-mentioned contact face can be ensured by increasing the density of the grooves. However, merely increasing the total area of the grooves by simply increasing the groove density is not very effective as a means of increasing the polishing rate. The reason for this is as follows: specifically, since the sum of the total area of the grooves and the contact area is equal to the area of the working surface of the polishing body, an increase in the total area of the grooves causes a decrease in the contact area, and (from the above argument) such a decrease in the contact area lowers the polishing rate. Accordingly, even if the density of the grooves is increased, such an increase in the total area of the grooves cancels the effect of increasing the fluidity of the polishing agent, and therefore cancels the effect that increases the polishing rate. A high groove density is not in itself sufficient to increase the fluidity while avoiding a decrease in the contact area; at the same time, the groove width must be narrowed. The polishing agent can be supplied to all parts of the contact face, and the polishing rate can be increased, by narrowing the groove width and reducing the groove pitch, so that the groove density is increased.
Here, what is important is the role of the grooves. The grooves not only have the function of forming projecting parts on the polishing body, and the function of ensuring the fluidity of the polishing agent by supplying the polishing agent to the projecting parts that constitute the contact face, but also the important function of discharging polishing debris or polishing particles in the polishing agent that have become aggregated (hereafter referred to as xe2x80x9caggregated polishing particlesxe2x80x9d) from the contact face. From this standpoint, it is better if the groove width is not too narrow. The reason for this is as follows: specifically, if the groove width is too narrow, the polishing debris or aggregated polishing particles will clog the grooves while being discharged; as a result, the discharge of the polishing debris or aggregated polishing particles to the outside of the working surface of the polishing body is interrupted, and the contact of such polishing debris or aggregated polishing particles with the object of polishing causes scratching during polishing.
For the above reasons, the groove pitch should be neither too coarse nor too fine, and the groove width should be neither too wide nor too narrow; this pitch and width have respective optimal values.
Here, (a+c) is the groove pitch; the pitch p of the grooves is determined by a trade-off between the mutually conflicting characteristics of favorable polishing agent fluidity and abundant contact area. As a result of experimentation, it has been determined that a value of 0.1 mm to 5.0 mm is desirable. As a result of similar experimentation, it has been determined that a value of 0.0 mm to 3.0 mm is desirable as the length b of the top sides of the projecting parts between the grooves. The lower limit of the depth d of the grooves is determined by the discharge characteristics of the polishing debris or aggregated polishing particles; it has been determined that a value of 0.1 mm or greater is desirable.
A fifth embodiment of the present invention which is used in order to achieve the second aspect is the first embodiment which is further characterized by the fact that the section of the recessed parts (groove parts) of the recessed and projecting parts has a shape that has curved portions.
If the section of the recessed parts (groove parts) of the recessed and projecting parts has a shape that has curved portions, the supply and discharge of the polishing agent are facilitated; furthermore, the size of the angle formed by the grooves and the working surface of the polishing member can be increased, so that the generation of parts with sharp angles in the working surface of the polishing member can be suppressed. As a result, scratching of the object of polishing can be effectively suppressed.
A sixth embodiment of the present invention which is used in order to achieve the second aspect is the fifth embodiment which is further characterized by the fact that the shape that has the curved portions satisfies the following conditions:
0.0 mmxe2x89xa6exe2x89xa63.0mm, 0.1 mmxe2x89xa6e+fxe2x89xa65.0mm, gxe2x89xa70.1 mm
wherein, e is the length of the top side of the projecting parts, f is the length of the top side of the recessed parts, and g is the depth of the recessed parts.
The reasons for limiting the respective numerical values in this manner are the same as the reasons for limiting the numerical values in the fourth embodiment.
A seventh embodiment of the present invention which is used in order to achieve the second aspect is any of the first through sixth embodiments which is further characterized by the fact that the recessed and projecting parts have a periodic structure of recesses and projections.
In the present invention, since the recessed and projecting parts have a periodic structure, working is simplified, and this working can be accomplished using automated working machinery.
An eighth embodiment of the present invention which is used in order to achieve the second aspect is any of the first through seventh embodiments which is further characterized by the fact that the non-foam resin has a Vickers hardness of 1.5 kgf/mm2 or greater, or a compressive Young""s modulus of 25 kgf/mm2 or greater.
One major special feature of hard non-foam polishing members is smoothness, i.e., efficient elimination of pattern step differences. When the hardness of a polishing member drops, the step difference elimination characteristics of this polishing member deteriorate. As a result, it has been found that residual step differences can be suppressed to a degree that there are no problems, and that both a high polishing rate and a good smoothness can be obtained, in cases where the Vickers hardness of the material of the polishing member is 1.5 kgf/mm2 (approximately 1.5xc3x97107 Pa) or greater, or in cases where the compressive Young""s modulus of this material is 25 kgf/mm2 (approximately 2.5xc3x97108 Pa) or greater.
A ninth embodiment of the present invention which is used in order to achieve the second aspect is a polishing apparatus in which an object of polishing is polished by causing relative motion between a polishing body and this object of polishing in a state in which a polishing agent is interposed between the polishing body and object of polishing; this polishing apparatus being characterized by the fact that the apparatus uses the polishing body of one of the first through eighth embodiments as a polishing body.
Since this polishing apparatus uses the polishing body of one of the first through eighth embodiments, the respective effects of the first through eighth embodiments can be obtained, so that the above-mentioned second aspect can be achieved.
A tenth embodiment of the present invention which is used in order to achieve the above-mentioned second aspect is a method in which an object of polishing is polished by causing relative motion between a polishing body and this object of polishing in a state in which a polishing agent is interposed between the polishing body and object of polishing; this polishing method being characterized by the fact that the method uses the polishing body of the eighth embodiment as a polishing body, and the fact that the method includes a stage in which the temperature of the polishing body is controlled.
The polishing rate is proportional to the contact area. However, contact between solids is generally a point contact. Since the non-foam polishing member of the present invention uses a hard material, the effective contact area is lower than a value that is simply calculated from the figures; accordingly, the polishing rate may also be lower than the expected value. Consequently, the temperature dependence of the hardness of the resin of the polishing pad material is utilized in order to adapt the projecting parts as a whole to the object of polishing. The hardness of the resin drops with a rise in temperature. The fit of the hardness of the polishing pad with respect to the object of polishing is improved by elevating the temperature or controlling the temperature. The polishing rate depends on the temperature, and increases with an increase in the temperature. Causes of this increase in the polishing rate include an increase in the reactivity of the slurry in addition to an increase in the effective contact area. Accordingly, the polishing rate can be increased, or a specified polishing rate can be maintained, by controlling the temperature of the polishing body.
A first embodiment of the present invention which is used in order to achieve the third aspect is a polishing body used in a polishing apparatus in which an object of polishing is polished by causing relative motion between a polishing body and this object of polishing in a state in which a polishing agent is interposed between the polishing body and object of polishing; this polishing body being characterized by the fact that the polishing body has grooves formed in its surface, the width W of the above-mentioned grooves at the surface is such that 0.1 mmxe2x89xa6Wxe2x89xa62.0 mm, the ratio VL of the volume of the region in which the grooves are formed to the volume of the polishing body including the region in which the grooves are formed is such that 0.1%xe2x89xa6VLxe2x89xa630%, and the polishing body is formed from a material in which the void region caused by foaming is 20% or less relative to the volume of the polishing body not including the region in which the grooves are formed.
In the polishing body, the material of the polishing body is a non-foam type or low-foam type material; accordingly, the polishing body shows extremely little wear due to use. Furthermore, dressing is either unnecessary or else is accomplished in a short time, so that there is no change in the groove structure due to wear; accordingly, extremely stable polishing characteristics can be obtained. As a result of these features, the frequency of polishing body replacement is reduced, so that the cost of polishing can be reduced. Furthermore, among the polishing characteristics, uniformity, smoothness and the polishing rate can be controlled according to the groove structure (groove width W, volume ratio VL) formed in the surface of the polishing body. Thus, the groove structure can be selected so that ideal polishing characteristics are obtained. As a result, the polishing yield can be improved, and the time required for polishing can be shortened, so that the cost of polishing can be reduced.
A second embodiment of the present invention which is used in order to achieve the third aspect is the first embodiment which is further characterized by the fact that the thickness D is such that 0.5 mmxe2x89xa6Dxe2x89xa65.0 mm.
As a result, among the polishing characteristics, uniformity, smoothness and the polishing rate can be controlled according to the thickness D of the polishing body; accordingly, the thickness can be selected so that ideal polishing characteristics are obtained. Consequently, the polishing yield can be improved, and the time required for polishing can be shortened, so that the cost of polishing can be reduced.
A third embodiment of the present invention which is used in order to achieve the third aspect is the first embodiment or second embodiment which is further characterized by the fact that the depth of the above-mentioned grooves is no more than three times the width W of the grooves.
As a result, there is no scratching of the polished surface of the object of polishing. Accordingly, the polishing yield can be improved, and the cost of polishing can be reduced.
A fourth embodiment of the present invention which is used in order to achieve the third aspect is any of the first through third embodiments which is further characterized by the fact that the shape of the grooves with respect to the surface is a spiral shape, concentric circular shape, lattice shape, triangular lattice shape, xe2x80x9cknittedxe2x80x9d shape, random shape or shape which includes two or more of the preceding shapes.
As a result, the polishing agent retention capacity at the surface of the polishing body is high, so that the polishing rate is increased, and the uniformity is also increased. Accordingly, the polishing yield is improved, and the time required for polishing is shortened, so that the cost of polishing can be reduced.
A fifth embodiment of the present invention which is used in order to achieve the third aspect is any of the first through fourth embodiments which is further characterized by the fact that the sectional shape of the grooves is a shape that has a curvature, a rectangular shape, a V shape or a polygonal shape.
As a result, scratching of the polished surface of the object of polishing is eliminated. Accordingly, the polishing yield is improved, and the cost of polishing can be reduced.
A sixth embodiment of the present invention which is used in order to achieve the third aspect is any of the first through fifth embodiments which is further characterized by the fact that the compressive elastic modulus K of the material is such that 0.1 GPaxe2x89xa6Kxe2x89xa62.0 GPa.
In the present means, since the material is not too soft, the amount of wear during polishing is small, so that the polishing body has a long useful life; furthermore, there is no deterioration in smoothness. Moreover, since the material is not too hard, there is no scratching of the object of polishing, and there is also no deterioration in uniformity.
As a result, the polishing yield can be increased in the case of a polishing body formed from a material whose compressive elastic modulus K is such that 0.1 GPaxe2x89xa6Kxe2x89xa62.0 GPa, so that the cost of polishing can be reduced.
A seventh embodiment of the present invention which is used in order to achieve the third aspect is any of the first through sixth embodiments which is further characterized by the fact that the chief component of the material comprises one or more resins selected from a set comprising epoxy resins, acrylic resins, polyester resins, vinyl chloride resins, polycarbonate resins and non-foam urethane resins.
As a result, there is little wear of the polishing body caused by polishing, so that the useful life of the polishing body is increased. Accordingly, the frequency with which the polishing body is replaced is reduced, so that the cost of polishing can be reduced.
An eighth embodiment of the present invention which is used in order to achieve the third aspect is any of the first through seventh embodiments which is further characterized by the fact that a first plurality of grooves that supply and discharge the polishing agent are further formed in the surface, and the grooves that supply and discharge the polishing agent form parts of the previously mentioned grooves, or are formed separately from the grooves.
As a result, since the polishing agent is uniformly supplied to the entire polished surface of the object of polishing, there is no deterioration in uniformity, and no deterioration in the polishing characteristics due to an increase in wear. Accordingly, the polishing yield can be increased, and the cost of polishing can be reduced.
A ninth embodiment of the present invention which is used in order to achieve the third aspect is any of the first through eighth embodiments which is further characterized by the fact that there is a transparent region in at least one portion of the polishing body.
As a result, the polished state of the polished surface of the object of polishing can be detected in situ during the polishing process by means of a device that observes the polished state via the opening part formed in the polishing platen and the transparent region of the polishing body. Accordingly, since the endpoint of polishing can be detected during the polishing process, the polishing yield can be increased, and the cost of polishing can be reduced. For example, vinyl chloride, etc., can be used as the material that constitutes the transparent region.
A tenth embodiment of the present invention which is used in order to achieve the third aspect is a polishing apparatus in which an object of polishing is polished by causing relative motion between a polishing body and this object of polishing in a state in which a polishing agent is interposed between the polishing body and object of polishing; this polishing apparatus being characterized by the fact that any of the first through ninth embodiments is used as the polishing body.
In this invention, since one of the above-mentioned first through ninth embodiments is used as the polishing body, the advantages of the respective corresponding polishing bodies can be obtained, so that the above-mentioned third aspect can be achieved.
A first embodiment of the present invention which is used in order to achieve the fourth aspect is a polishing body used in a polishing apparatus in which an object of polishing is polished by causing relative motion between a polishing body and this object of polishing in a state in which a polishing agent is interposed between the polishing body and object of polishing; this polishing body being characterized by the fact that recessed and projecting structures of two or more different types are formed periodically or aperiodically in the surface of the polishing body.
In the above-mentioned polishing body, two or more types of recessed and projecting structures are formed; accordingly, in regard to the polishing characteristics, areas in which the uniformity is good and areas in which the smoothness is good coexist in accordance with the recessed and projecting structures. As a result, both the uniformity and the smoothness are improved.
Specifically, a hard polishing body and a soft polishing body can be caused to coexist in apparent terms in the same polishing body by forming two or more types of recessed and projecting structures on the surface of the polishing body without modifying the laminated structure of the polishing body or the polishing head. Accordingly, a polishing body and a polishing method using this polishing body can be provided which make it possible to improve the polishing characteristics of uniformity and smoothness, which are generally said to be in a trade-off, even if a conventional polishing apparatus is used. This also offers the advantage of making it possible to increase the yield of the semiconductor manufacturing process without incurring any expense in the polishing process.
A second embodiment of the present invention which is used in order to achieve the fourth aspect is the first embodiment which is further characterized by the fact that two or more recessed parts of the recessed and projecting structures and two or more projecting parts of the recessed and projecting structures are formed within the regions in which recessed and projecting structures of the same type are formed.
As a result, the uniformity and smoothness are improved even further.
A third embodiment of the present invention which is used in order to achieve the fourth aspect is the second embodiment which is further characterized by the fact that the recessed and projecting structures comprise two types of recessed and projecting structures, i.e., a first recessed and projecting structure and a second recessed and projecting structure, the recessed parts of the first recessed and projecting structure and the recessed parts of the second recessed and projecting structure are grooves, and the width of the projecting parts of the first recessed and projecting structure is two or more times the width of the projecting parts of the second recessed and projecting structure.
As a result, the regions of the polishing body in which the first recessed and projecting structure with wide projecting parts is formed function in a manner comparable to that of a hard polishing body, and selectively polish the projecting parts of the recessed and projecting pattern during the polishing of an object of polishing that has such a recessed and projecting pattern, so that the smoothness is improved. Meanwhile, the regions of the polishing body in which the second recessed and projecting structure with narrow projecting parts is formed function in a manner comparable to that of a soft polishing body, so that the polishing body performs polishing while conforming to any warping of the object of polishing or irregularity in the film thickness generated during the formation of any film on the surface of the object of polishing. As a result, the uniformity is improved.
A fourth embodiment of the present invention which is used in order to achieve the fourth aspect is any of the first through third embodiments which is further characterized by the fact that the plan shape of the polishing body is circular, and the regions in which the recessed and projecting structures of the same type are formed are disposed in the form of concentric circles.
As a result, the uniformity and smoothness are further improved.
A fifth embodiment of the present invention which is used in order to achieve the fourth aspect is any of the first through third embodiments which is further characterized by the fact that the regions in which the above-mentioned recessed and projecting structures of the same type are formed are disposed in a lattice-form configuration.
As a result, the uniformity and smoothness are further improved.
A sixth embodiment of the present invention which is used in order to achieve the fourth aspect is any of the first through fifth embodiments which is further characterized by the fact that grooves that supply and discharge the polishing agent are further formed in the surface of the polishing body.
As a result, since the polishing agent is uniformly supplied to the entire surface of the object of polishing, there is no deterioration in the uniformity, or deterioration in the characteristics of the polishing apparatus as a result of increased wear.
A seventh embodiment of the present invention which is used in order to achieve the fourth aspect is any of the first through sixth embodiments which is further characterized by the fact that the Vickers hardness k of the polishing body is such that 2.5 (kgf/mm2) less than k less than 30 (kgf/mm2).
As a result, the uniformity and smoothness are further improved.
An eighth embodiment of the present invention which is used in order to achieve the fourth aspect is any of the first through seventh embodiments which is further characterized by the fact that the polishing body is constructed from a first layer in the surface of which the recessed and projecting structures are formed, and a second layer which is disposed beneath the first layer and to which the first layer is laminated, and the elastic modulus of the second layer is greater than the elastic modulus of the first layer.
As a result, the uniformity and smoothness can be improved in a polishing body with a laminated structure as well.
A ninth embodiment of the present invention which is used in order to achieve the fourth aspect is a polishing apparatus in which an object of polishing is polished by causing relative motion between a polishing body and this object of polishing in a state in which a polishing agent is interposed between the polishing body and object of polishing; this polishing apparatus being characterized by the fact that any of the first through eighth embodiments is used as the polishing body.
In this invention, since the polishing body of one of the first through eighth embodiments is used, the respective effects described for these inventions can be exhibited, so that the above-mentioned fourth aspect can be achieved.
An invention of the present invention which is used in order to achieve each of the first through fourth aspects is a semiconductor device manufacturing method which is characterized by the fact that this method includes a process in which a wafer is polished using at least one method or apparatus among the polishing methods of the sixth through ninth embodiments to achieve the first aspect, and the polishing apparatuses of the tenth and eleventh embodiments to achieve the first aspect, the ninth and tenth embodiments to achieve the second aspect, the tenth embodiment to achieve the third aspect and the ninth embodiment to achieve the fourth aspect.
In this invention, since polishing methods or apparatuses with respective advantages are utilized, wafers can be polished in accordance with the above-mentioned first through fourth objects. Accordingly, semiconductor devices can be manufactured with a good precision, yield and throughput.